docs: def _internal_reschedule(callback, retry=3, sleep_time=constants.DEFAULT_SLEEP):
          """
          workaround method for internal_run_container method
          It sometimes fails because of Dbus or whatever, so try to start it moretimes
  
          :param callback: callback method list
          :param retry: how many times try to invoke command
          :param sleep_time: how long wait before subprocess.poll() to find if it failed
          :return: subprocess object
          """
          for foo in range(retry):
              container_process = callback[0](callback[1], *callback[2], **callback[3])
              time.sleep(sleep_time)
              container_process.poll()
              rcode = container_process.returncode
              if rcode is None:
                  return container_process
          raise ConuException("Unable to start nspawn container - process failed for {}-times".format(retry))